Published Online
on August 21, 2008

A more recent version of this article appeared on November 1, 2008

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Submitted on December 21, 2007
Revised on March 17, 2008
Accepted on March 31, 2008

Quantitative Assessment of Core/Penumbra Mismatch in Acute Stroke. CT and MR Perfusion Imaging Are Strongly Correlated When Sufficient Brain Volume Is Imaged

Pamela W. Schaefer MD^*; Elizabeth R. Barak MD; Shahmir Kamalian MD; Leila Rezai Gharai MD; Lee Schwamm MD; Ramon Gilberto Gonzalez MD, PhD; and Michael H. Lev MD

From the Departments of Radiology (P.W.S., E.R.B., S.K., L.R.G., R.G.G., M.H.L.), and Neurology (L.S.), Massachusetts General Hospital, Harvard Medical School, Boston, Mass.

^* To whom correspondence should be addressed. E-mail: pschaefer{at}partners.org.

Background and Purpose—Our purpose was to determine (1) the correlation between quantitative CT and MR measurements of infarct core, penumbra, and mismatch; and (2) whether the difference between these measurements would alter patient selection for stroke clinical trials.

Methods—We studied 45 patients with acute middle cerebral artery stroke imaged a mean of 3.8 hours after onset (range, 0.48 to 8.35 hours) who underwent CT perfusion and MR diffusion (DWI)/perfusion imaging within 3 hours of each other. The DWI and MR-mean transit time (MTT) abnormalities were visually segmented using a semiautomated commercial analysis program. The CT-cerebral blood volume) and CT-MTT lesions were automatically segmented using a relative cerebral blood volume threshold of 0.56 and a relative MTT threshold of 1.50 on commercially available software. Percent mismatch was defined as [(MTT-DWI)/DWI volume]x100. Pearson correlation coefficients were calculated.

Results—There were significant correlations for DWI versus CT-cerebral blood volume lesion volumes (r²=0.88, P<0.001), for MR-MTT versus CT-MTT lesion volumes(r²=0.86, P<0.001), and for MR-MTT/DWI versus CT-MTT/CT-cerebral blood volume mismatch lesion volumes(r²=0.81, P<0.001). MR perfusion and CT perfusion agreed for determining: (1) infarct core < versus 100 mL in 41 of 45 (91.1%); (2) MTT lesion size < versus >2 cm diameter in 42 of 45 (93.3%); (3) mismatch < versus >20% in 41 of 45 (91.1%); and (4) inclusion versus exclusion from trial enrollment in 38 of 45 (84.4%) patients. Six of 7 disagreements were due to inadequate CT coverage.

Conclusion—Advanced MR and CT perfusion imaging measurements of core/penumbra mismatch for patient selection in stroke trials are highly correlated when CT perfusion coverage is sufficient to include most of the ischemic region. Although MR is currently the preferred imaging method for determining core and penumbra, CT perfusion is comparable and potentially more available.

Key words: acute ischemic • acute stroke • CT • MRI • penumbra • perfusion CT imaging • perfusion MR imaging

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